C. trachomatis (CT) is the most common sexually transmitted bacterial infection with an estimated 100 million annual cases worldwide. Arising in the endocervix, in ~10% of infected women CT ascends to the endometrium and oviducts where it can cause symptomatic or subclinical pelvic inflammatory disease, leading to chronic pelvic pain, infertility, and ectopic pregnancy. Antibiotic treatment is limited because >70% of infections are asymptomatic, and women may present for treatment after irreversible oviduct damage has occurred. The goal of this Sexually Transmitted Infections (STI) Cooperative Research Center (CRC) U19 proposal, ?University of North Carolina-Chlamydia Vaccine Initiative (UNC-CVI STI CRC),? is to develop a novel vaccine that prevents CT ascension in the female genital tract, eliminating CT-associated PID and infertility. The ultimate goal is to develop a vaccine regimen that fully prevents productive CT infection. To help achieve these goals, the proposed Clinical Core, based at the University of Pittsburgh, will work closely with the scientists and staff of Research Project 1 and Research Project 3 to provide the comprehensive clinical research support needed to, respectively, evaluate CT antigens in women and identify biomarkers of disease risk or susceptibility during CT infection. The core will conduct thorough, sensitive screening and evaluation of reproductive-aged women with or at-risk for STIs; safely and efficiently enroll individuals and ensure that recruitment and retention protocols enroll a diverse clinical population from an array of ethnic and socio- economic backgrounds for the two projects; collect information and clinical specimens from participants; and conduct initial laboratory testing of samples for STI pathogens. Achievement of the core?s goals will be facilitated in three critical ways. One, the core will use the clinical sites and some of the same personnel that participated in a previous core-supported project, the T Cell Response Against Chlamydia (TRAC) Study of the University of Pittsburgh STI CRC. These sites -- the Allegheny County Health Department Sexually Transmitted Diseases Program and the Ambulatory Clinic at Magee-Womens Hospital (both for enrollment), and the Reproductive Infectious Diseases Research Unit (for follow-up clinical activities, also in Magee- Womens Hospital) ? are a five minutes? drive apart. Two, the core will employ the recruitment, retention and data collection procedures from the TRAC Study, which met all recruitment targets and had high retention. Three, banked samples from TRAC led to preliminary data for this U19 proposal, and they will supplement the samples to be gathered by the core to complete Projects 1 and 3. The successful recruitment and retention of UNC-CVI clinical research participants and the data originating from the human samples collected and distributed by the core to Center scientists will greatly ensure the success of Projects 1 and 3 and will significantly contribute to the UNC-CVI?s long-term goal to develop a preventative vaccine for C. trachomatis.